Froth flotation apparatus



Feb. 18, 1941. c. R. xNGALLs Erm.

FROTH FLOTATIN APPARATUS Filed July 19. 1939 5 Sheets-Sheet 1 A TT ORNE YS Feb.' 18, 1941. c. R. INGALLS ETAL 2,232,388

FROTH FLOTATION APPARATUS. Filed July 19, 1939 5 Sheets-Sheet 2 ATTORNEYS Feb.l 18, 1941.l

C. R. INGALLS ETAL FROTH FLOTATION APPARATUS Filed July 19, 1939 5 Sheets-Sheet 5 A TTORNEYS Feb. 18, 1941. c. R. xNGALLs ETAI.

FROTH FLOTATION APPARATUS Filed July 19, 1939 5 Sheets-Sheet 4 ATTORNEYS Feb. 18, 1941.

c. R. rNGALLs ETAL FROTH FLOTATION APPARATUS Filed July 19, 1939 5 SheetsfSheet 5 fa- [319 l (33N ENToRS BY AAW/M4 Z. WW

ATTORNEYS Patented Feb. 18, 1941 Fao'rn rLoTA'rIoN APPARATUS Christopher R. Ingalls, Alameda, Carl F. Williams, San Mateo, and Lawrence L. Mayer, Palo Alto, Calif., assignors to Minerals Separation North American Corporation, New York, N.. Y., a corporation ofMaryland I Application July 19, 1939, Serial No. 285,292

8 Claims.

The present invention relates to apparatus for the flotation concentration of comminuted materials and is herein illustrated and particularly described in a form especially adapted for use in the froth flotation of ores, it being understood that the invention may be usefully applied to the flotation treatment of various other materials including coal pand other nonmetallic minerals, slimes, trade wastes, sewage,

lll wool grease, sawdust mixtures, starch-gluten mixtures, chemicals of various kinds, etc.

An object of the invention is to provide an apparatus of the character mentioned, which is simple in construction, low in cost of manu- 15 facture, and efficient in operation. Another object of the invention is to provide an apparatus of the character I mentioned, which requires little attention to maintain its operation at high 'mechanical and metallurgical efficiencies even 2o under varying mill conditions, which has a low power consumption, and which is not subject to clogging by settling of the solids in the pulp 4upon failure of the'power supply or shutting down for any other reason Still another object 25 of the Ainvention is to provide an apparatus of the character mentioned, which allows easy and rapid passageof unduly coarse orrheavy matter,

thereby insuring against the possibility of itsV clogging the apparatus. A further object of the 3o invention is to provide an apparatus of the character mentioned, which is structurally such as to cause the material treated to be thoroughly circulated with the view to effecting its'proper conditioning prior to flotation. A still further 3p object of the invention is toprovide an apparatus of the character mentioned, which draws ln sufficient air for froth flotation, without recourse to such extraneous devices as blowers or fans, and causes the air to be effectively disseminated 40 in the material prior to flotation.

To the above ends, the invention contenirplates a dotation apparatus comprising atleast one of a series of cells each of which is equipped with a specially constructed impeller located at 45 a substantial distance from the bottom in the vicinity' of a balie dividing the cell into a lower zone of agitation and an upper zone of separa- `tion, thus placing the impeller close to the top of theagitation zone instead ,of in the vicinity 50 of the bottom of said zone and of the whole cell, the impeller being mounted on a hollow spindle which is open to the atmosphere at itsupper end and provides a passage for the downward ow of air into the agitation zone.v The construction of the impeller is such that a downward thrust or .a combined radial end downward thrust is caused to be exerted on the material treated, which is thus effectively circulated in the agitation zone and at the same time is effectively admixed with air drawn downwardly through the spindle by the action of the impeller, the construction of the batlie being such as tapermit the material thus conditioned in the agitation zone to rise into the comparatively quiescent upper zone wherein it is subjected to flotation separation. The apparatus comprises any vnumber of such cells connected with one another through suitable openings located in whole or in part below the bailles.

One of the important advantages resulting from the present invention is decreased power consumption due to the fact that the-impeller, instead of being located as usual at the bottom of the lower zone of agitation, is located near the top of that zone where air is introduced into the pulp against a lower hydrostatic head than is the case when air is introduced as usual near the bottom of the lower zone of agitation. Another important .advantage results from the fact that the impeller is located so high in the zone of agitation that it is not likely to be buried when the solids in the pulp settle in the cell due to stopping of the impeller resulting from power-failure or shut-down. By reason of this last mentioned fact, it is possible, after powerfailure or shutdown, to resume operation ot the apparatus without digging out or iiushing out the settled solids as is'often necessary in flotation machines of the prior art characterized by the fact that their impellers are located 35 near the bottom of the zone of agitation. Other advantages of the invention will be obvious to those skilled in the art.

The invention and the objects thereof will be understood from the following description takenl 4.o

v in conjunction with the accompanying drawings in which Fig. l; is a transverse sectional elevation of an apparatus embodying the invention; Fig. 2 is a longitudinal sectional view taken on the line 2X--2X of Fig. l, certain parts being broken 45 away and other parts omitted; Fig. 3 is a plan view of the 'apparatus as it appears in Fig. 2; Figs. 4 and 5 are, respectively, a transverse'section and a bottom view of our preferred form of impeller; Figs. 6 and '7 are, respectively, a 50 transverse section and a bottom viev.r of a modied form of impeller; Fig. 8 is a transverse sectional view of a modied form of flotation cell; Fig. 9 is an enlarged sectional view of certain details embodied in the modication shown in Fig. 8, inclusive of its two impellers; Fig.A 10 is a bottom view o1' the lower impeller included in the modification shown in Fig. 8, a portion of the lower disc being broken away; Fig. 11 is a transverse sectional view of another modied form of notation cell; and Figs. 12 and 13 are, respectively, edge .and side elevations of an alternative form of adjustable froth discharge lip.

Referring to Figs. 1 to 3, the apparatus shown therein comprises a trough or box-like vessel having a horizontal bottom wall I, two side walls 2 and 3,-and two end walls 4 and 5, said vessel being divided into a series of connected or communicating pulp-agitatiing and froth-separating cells 6, l, and 8. Any number of intermediate cells I may be interposed in series between the end cells. 8 and 8, but for convenience of description only two such intermediate' cells are herein illustrated, one being shown in part and the otherin its entirety.

At the feed end of the apparatus, as viewed at the left of either Figs. 2 or 3, is a feed box 9 which is formed in part by the end wallI 4 and forms a'passage I0 terminating at a lower opening II in the end wall 4. 'I'he ore pulp is`introduced through such passage and opening into the first cell 6. The apparatus is partitioned into the several cells, 6 to 8 by means of transverse walls I2 extending crosswise to meet the side walls 2 and 3. Thus, the first cell 6 is bound' ed by one such partition Wall in conjunction with the end wall 4, the side walls 2 and 3, and the bottom wall I; the intermediate cells 'I are each bounded by two such partition walls in conjunction with the side walls 2 and 3 and the bottom wall I; and the last cell 8 is boundedY by one such partition wall in conjunction with the end wall 5, the side walls 2 and 8, and the bottom wall I. As shown, the partition walls I2 are pro- 40 vided with comparatively large openings I3,

through which the ore pulp may readily pass from one cell to the next. At the discharge end of the apparatus, as viewed at the right of either` Figs. 2 or 3, is a tailings discharge and levelregulating unit I4 to be hereinafter more particularly described. `The end wall 5 also serves as the front wall of such unit, into which the tailings or residues from the end cell 8 are directed through a lower opening I5 in such wall.

o0 Each of the several cells 6 to 8 isdivided by means of a baille I6 into a lower zone of agitation and aeration and an upper zone of froth formation and separation. These battles may be of cast iron or steel, or in any other suitable material. Their construction should be such as to permit upward flow of the ore pulp and at the same time confine the swirl of the ore pulp to the lower zone in each cell. Each of the bailles I6 as herein shown comprises a plurality of cross w members Ilia arranged in layers spaced from one another by longitudinal members ISb, but it is understood that the invention is not limited to this particular form of bale, any one of various other forms well known in the art being avail- 55 able for use in the apparatusv of the invention.

'I'he baies I 6' should be set at a substantial distance from the bottom of the cells, their vertical position being largely determined by the nature of the material to undergo treatment and the efficiency with which the impeller means to' be hereinafter described effects circulation in the lower zones of agitation. In the case of light pulps or of high impeller speeds, for example, the bailies I6 may be set so that such zones occupy the greater part of the cells.` It is thus apparent that the several cells 6 to 8 may have greater over-all depth than the conventional type of flotation cell. This notonly results in increased capacity of the apparatus, but also permits more effective conditioning of the ore 8 pulp prior to`iiotation. In setting the position of the batlles I6, of course, the distance above them should be suicient to produce the comparatively quiescent zones needed for the formation and maintenance of the proper depth of froth or float. As shown in the drawings, the bailles I6 are preferably located at a distance from the bottoms of the cells of about one-half of the cell depths, though as explained above this distance may be substantially increased. l

The inlet and 'outlet openings II and Iiiy in the end walls of the apparatus, and the intermediate openings I 3 in the partition walls, may be of any suitable shape or size. However, the inlet and outlet openings II and I5 should be 20 formed so their entire areas are located below the bailles I6. As to the intermediate openings I 3, they' should at least in part be formed below the bailles I6, but may extend all the way up to the top of the several cells. If desired, suitable means (not shown) may be associated with the intermediate openings I3 for controlling their effective areas. Also, to facilitate the passage through the apparatus of unduly coarse or heavy matter in the pulp, the partition walls may be spaced at their lower edges from the bottom wall to provide narrow oor openings I'I extending all the way across the apparatus, as best shownin Fig. 1. Other openings I8 may be provided in either one of the side walls of the apparatus for the purpose of drainage, these openings being associated with any suitable closure means, which are herein shown as comprising plugs I9 adapted for insertion into nipples 20.

To guard against the abrasive action of the agitated pulp, each of the respective lower zones of the several cells 6 to 8 may be lined with suitable wear-resisting material 2| such as cast iron or rubber. 'I'he upper edges of such lining aiOrd convenient rests for the baiiles I6.

Associated with each of the several cells 6 to 8 is a vertical hollow shaft or spindle 22 rotatably supported by bearings 23 carried by an overhead frame 24. The spindles 22 extend through the baiiles IB'and carry at their lower ends rotary impellers 25 to be' hereinafter more particularly described. Rotation of the spindles 22 may be eilected in any suitable manner. As shown, the spindles 22 may be fitted at their upper ends with pulleys 28 connected by belts 21 with the pulleys 28 of a motor 29, which may conveniently be mounted on a side bracket 3U.

'Ihe impellers 25 are so designed that by Atheir rotary action, downward forces, or both radial and downward forces, are produced on the surrounding pulp, with the result that the latter is caused to be eil'ectivelyvcirculated in the lower agitation zones. In this respect, the impellers 25 differ from the impellers of the prior art, whose only forms have been suchas rto produce simple radial motion or combined upward and radial motion of the treated pulp. The impellers 25 provide communication therethrough from the interior of the hollow spindles 22 so-that, by the rotary action o'f the impellers, air is induced to ilow down these spindles into the pulp and thusbe' effectively admixed with the latter in the lower agitation zones.

Referring particularly to Figs. 4 and 5, the impellers 25 are seen to comprise a disc 3| pro- 75 vided with a smooth upper surface 3la, their attachment to the hollow spindles 22 being effected by any suitable means, which may in. clude an upper hr?) 32 centrally formed from such upper surface. Formed on the lower side of the disc 3l are the agitating blades 33 which, in our preferred form of impeller illustrated in Figs. 4 and 5, meet, at the centerof the disc where they are set perpendicularly to its lower side, the central portion of the disc 3| being hollowed out to the inner diameter of the hub 32 to provide a plurality of segmental openings 34 all slightly removed from the disc center for the passage of air into the pulp. From the disc center, the blades 33 extend in curved directions toward the periphery and atu the same time become tilted, their inclination at the periphery being such that their lower surfaces 33a make an angle of, say, 60 'degrees from the vertical. By thisl form of impeller, as we have found, the induced airv as a result of its passage in separate streams through the several openings it is most effectively disseminated inthe agitated pulp in the respective lower zones of the several cells, aside from which the mixture of agitated pulp and induced air is most effectively circulated and aerated in such zones as a result of its be ing projected obliquely downwards toward the bottom of the apparatus.

It is understood, of course, that the invention is not limited to the particular form of irnpeller shown in Figs. 4 and 5. Any other form of impeller may be used which is adapted to exert a downward thrust on the agitated pulp and provides passage of air into such pulp. In the modified form of impeller shown in Figs. 6 and 7, a disc di and upper hub 32 are again used, but the blades 35 formed on the lower side of the disc 3l' no longer meet at the disc center, the construction of these blades being such that they extend outwardly from points slightlyl beyond the central opening 36 through the disc 3l' and upper hub 32. A form of cell in which this form of impeller is particularly useful will be hereinafter described. i

Like the bailies i6; the impeller should be set at a substantial distance from the bottom of the apparatus. It is our discovery that, as this distance is increased in a cell of given dimensions, the amount of air induced at a given speed tends to increase, while the power required to rotate the impellers decreases simultaneously. Preferably, the impellers should be set just below and close to the baffles it and therefore at a considerable distance above the bottom of the cell.

Referring to Fig. 2, the amount of air passing through the spindles 22 may be controlled. by a movable plug 3l, which may be of metal, felt, or of any other suitable material. A threaded member 38, adjustably supported by a bracket 39 secured to the frame it, carries the plug il, a handwheel fill and a locirnut it being provided on the member it to adjust and lock theplug di in any desired position. of course, may be used to regulate the air entering the spindles mi.

As best shown in Fig. l, the side-wall ii oi the apparatus slopes outwardly above the baiiles it and is otherwise formed to provide upper openings dt for the discharge of the flotation concentrates from the several cells. Associated with the openings d2 are the usual overflow lips d3, the height of which may be controlled by the number of superimposed slats 44 positioned within guide any other means, A

members 43 provided at either side o f the openings 42. It will be .understood that, inasmuch as the overflow lips 43 may be placed at various horizontal levels, the desired depth of froth may be maintained in each of the several cells. When passing over the lips 43, the flotation concentrates from the several cells may-be directed into a collecting launder 46, as shown in Fig. 1.

To facilitate the removal of the flotation concentrates from the several cells, wipers or paddles 41 are provided which are secured to revolving members 48 on a shaft 49, there being one of such wipers or paddles for each of the several cells. As shown in Fig. 3, the shaft 49 is journalled in bearings 50 suitably located on the framework of the apparatus, its rotation being effected by suitable mechanical means (not shown). Since it may be desired to vary the sweep of the wipers or paddles di, they are provided with elongated openings 5| by means of which they may be adjustably secured to their supporting members d3. 'f

In some cases, it may be desired to separate the concentrate overflow of one cell or group of cells from that of another cell .or group of cells. As shown in Fig. l, the launder it may to this end include two collecting compartments or troughs 52 and t3 separated from one another by a common walld equipped with aprons 55 adapted to swing outwardly either into a position (shown in full lines) closing the compartment 52 or into a position (shown in dotted lines) closing the compartment b3, there being one of such aprons for each ofthe several cells. By properly positioning ythe several aprons b5, the flotation concentrates from ythe several cells may thus be collected in part through the trough 52 and in part through the trough 53, which permits returning either of these divided portions of the flotation concentrates to the circuit, if desired.

Material to undergo treatment in flotation'apparatus often requires its introduction against hydraulic head, as in the return of middlings toward the feed end of such apparatus. Fig.- 3 shows a modified form of cell which may be advantageously employed in such cases. Asshown, this cell has a bottom opening 56 through which the ore pulp is introduced by the centrifugal pumping eiect of an additional impeller till. As before, a hollow spindle bd is employed which is fitted with a down-thrusting impeller 5t below the baffle it, but in this instance the spindle 5t is made toextend a considerable distance .into thev impeller 5l located close to the cell opening tt. The impeller t@ is similar in construction to the one shown in Figs. 6 and 7. as shown in Fig. 9, it has down-facing blades tt -dcated in cooperative relation to openings ti formed through the wall of the spindle tt, which is closed at its lower end by a plug tit, whereby air is entirely induced into the pulp through the openings 3 l The lower impeller bl may take any one of various forms.-

,prior to separation in the upper flotation z one.

'Referring to Fig. l'l, the modified form of cell shown therein merely differs from the cells hereinbefore described in that the upper part is conagitation zone and carries at its lower end the structed in double spitz-kasten form. It is thus seen to include a side wall 61 identical in shape to the side wall 3 and`likewise associated with an adjustable dischargelip 43 and a revolving paddle l1, the flotation concentrate being discharged into the two collecting launders 46 on either side of the cell. It is understood, of course, that a number of such cells in series may be used in the same manner as in the apparatus of Figs. 1 to 3. If desired, the various forms of cells which have been described may be suitably altered to include the metal overflow lip 68 shown in Figs. 12 and 13. As shown, this lip may be formed with elongated Y openings 69 by means of which it may be adjustably secured to the apparatus wall 18. This form of discharge lip may. of course., also be used on either one or both sides of the apparatus.

Referringto Figs. 2 and 3, the tailings discharge and level-regulating unit Il is formed by the end wall 5 of the apparatus in conjunction with a bottom wall 1|, side walls 12 and 13, and an end wall 14, a lower opening being provided in the end lwall 14 for the discharge of the tailings into a collecting launder 16. A transverse wall -11 divides the u nit into an'upcast compartment 18 and a downcast compartment 19, a lower opening 80 iitted with a conduit 80a being formed in the transverse wall 11 for the discharge of coarse sands from the upcast compartment 18. The transverse wall 11 is associated with a Weir 8|, the height of which may be controlled by the number of superimposed slats 82 positioned withl in the side members 83. It will be understood that, inasmuch as the weir lip 8l may be set at various horizontal levels, the desired depth of pulp may be maintained in the apparatus. The tailings from the end cell 8 pass by way of the opening I5 into the upcast compartment 18, flow over the weir 8| into the downcast compartment 19, and are finally discharged by way of the opening 15 into the launder 16; while the solids too coarse or too heavy to rise in the upcast compartment 18 are directlyV discharged into the launder 16 by way of the conduit 88a and opening such as float-operated valve or the like, may be employed in the apparatus of the present invention.

As the pulp progresses, from left n to right through the apparatus as viewed in Figs. 2 and 3,

lit is obviously successively acted upon in the several cells 6 to 8 so that flotation concentrates are removed from their respect upper zones, while the tailings tlow from one cell to the next until finally discharged through the level-regulating unit Il, as above explained. Y.

A particularly advantageous feature of the apa paratus of the present invention is the fact that, coincidentally with the agitation of the material under treatment therein, there is set up a circulation of this material with the result that it is thoroughly aerated without the wasteful expendiure of power and without the settling out of solid matter in the bottom of the apparatus.

It is understood that the invention is not limited to any particular number of flotation cells. As few as one only may be employed, which single flotation cell may be associated with the feed box 9 at one end and with the discharge unit I4 at the other, as will readilyybe understood from the foregoing description.

What is claimed is:

1. In a flotation cell, a baille located at a distance from the bottom of the cell not substantially less than one-half the depth oi' the cell and 15. Any other means of pulp level regulation,v

dividing it into a lower zone of agitation and an upper zone of separation, a vertical hollow spindle open at thetop to a supply of air or gas and extending through said, baille into the agitation zone, and an impeller mounted on said 5 spindle .lustv below and close to said bafileandA constructed Ito exert a downward thrust on the material treated in the cell, the interior of said spindle communicating with the agitation zone through said impeller.

2. In a flotation cell, a baille located at a distance from the bottom of the cell not substantially less than one-half the depth of the cell and dividing it into a lower zone of agitation and an upper zone of separation, a vertical hollow spinl5 dle open to the atmosphere at its upper-end and extending a slight distance through said baille into the agitation zone, and an impeller mounted on the lower end of said spindle just below and close to said baille and having down-thrust- 20 ing blades meeting at its center, the interior of said spindle communicating with the agitation f zone by openings formed between said impeller blades.

3. In a flotation cell, a baille located at a distance from the bottom of the cell not substantially less than one-half the depth of the cell and dividing it into a lower zone of agitation and an upper zone of separation, a vertical hollow spindle open to the atmosphere at its upper end and extending through said baille into the -agitation zone, and an impeller mounted on said spindle just below and close to said baille and comprising a disc provided with blades on its lower side progressively tilting in curved directions toward 85 its periphery, the interior of said spindle communicating with the agitation zone through said impeller. 4. In a dotation cell, a baille located at a distance from the bottom of the cell not substantially less than one-half the depth of the cell and dividing it into a lower'zone of agitation and an upper zone of separation, a vertical hollow spindie open to the atmosphere at its upper end and extending a slight distance through said baille into the agitation zone, and an impeller mounted on 4the lower end of said spindle just below and close to said baille and comprising a disc provided with blades on its lower side progressively tilting in curved directions from a perpendicular setting at its center to a maximum inclination at its periphery, the interior of said spindle com- `municating with the agitation zone through y openings formed between said impeller blades.

5. A flotation apparatus partitioned into a plurality of cells comprising baiiles located at a distance from the bottoms of the cells not substantially less than one-half of the depths of the cells and dividing them into lower zones of agitation and upper zones of separation, vertical hollow spindles open to the atmosphere and extending through said baflles into the agitation zones, and impellers mounted on said spindles just below and close to said baiiles and constructed to exert a downward thrust on the material treated in the cells, the hollow interiors of said spindles communicating with the agitation zones through said impellers, said cells communicating with one another through a plurality of openings in the partitions between said cells, the upper openings being close to and just belowsaid batlles and directly in line with said impellers and the other openings being at the bottoms of the cells.

6. A flotation cell comprising a bottom wall provided with an opening for introduction ofthe 75 material 1to be treated in the cell, a baille located at a substantial distance from said bottom wall and dividing the cell into a lower zone of agitation and an upper zone of separation, a vertical shaft extending through said baille into the agitation zone, an upper impeller mounted on said shaft below but in the vicinity of said baile vand constructed to exert a downward thrust on the material in the cell, said shaft having a longitudinally extending air passage communicating with .the agitation zone through' said upper impeller, and a lower impeller mounted on said shaft in the vicinity of said bottom wall opening and constructed to introduce the material to be treated by centrifugal action into the cell.

'7. A flotation cell comprising a bottom wall provided with an opening for introduction of the material to be treated in the cell, a baffle located at a substantial distance from said bottom wall and dividing the cell into a lower zone of agitation and an upper zone of separation, a vertical shaft extending through said bafe into the agitation zone, an upper impeller mounted on said shaft below but in the vicinity of said baille and provided with down-facing bladesv exerting a downward thrust on the material in the cell, said shaft having' a longitudinally extending air passage communicating with the agitation zone by openings located in cooperative relation to said down-facing blades, and a lower impeller mount- .ed on said shaft in the vicinity of said bottom Wall opening and constructed to introduce the material to be treated by centrifugal action into the cell.

8. A notation cell comprising a bottom wall provided with an opening for introduction of the material to be treated in the cell, a baiile located at a substantial distance from said bottom wall and dividing the cell into a lower zone of agitation and an upper zone of separation, a vertical shaft extending through said baille into the agitation zone, an upper impeller mounted on said shaft below but in the Vicinity of said baille and constructed to exert a downward thrust on the material in the cell, said shaft having a longitudinally extending air passage communicating with the agitation zone through said upper impeller, and a lower impeller mounted on said shaft in the vicinity of said bottom Wall opening and constructed to introduce the material to be treated by centrifugal action into the cell, said lower impeller having a centrally apertured lower disc for directing the material to be treated from said bottom wall opening.

CHRISTOPHER R. INGALLS. CARL F. WILLIAMS. LAWRENCE L. MAYER. 

